Method of controlling lubrication of continuous casting



Feb. 25, 1958 H. B. OSBORN, JR 2,

METHOD OF CONTROLLING LUBRICATION 0F CONTINUOUS CASTING Filed Jan. 2a, 1955 IN V EN TOR.

HARRY a OSBORN, JR.

ATTORNEY Unite METHOD or CQNTROLLING LUnRIcArioN' F CONTINUOUS CASTING This invention pertains to the art of'the continuous casting of metals into ingots, and more particularly to method and'apparatus for controlling the lubrication 'of the ingot as it passes through the mold cavity.

In the artof the continuous castingof metals an elongated Water-cooled vertically extending mold cavity is normally provided open at both the top and the bottom. Molten metal poured into the top of the mold moves downwardly as its heat is removed into the sides of the mold, and the metal congeals and is removed from the bottom of the mold as a solid bar oringot. One of the problems in such continuous casting has been that of properly lubricating the cast metal relative to the walls oi the mold. If too much lubricant is employed, improper cooling results, there. is a waste of lubricant, and oftentimes the surfaces'of the ingots are inferior. If too little lubricant is employed, there'is danger of the surface of the ingot tearing due to seizure with 'thewalls of the'mold, together with the even greater dangerof having the ingot freeze up in the mold itself. To remove 'a frozen ingot is an extremely expensive operation. 7 Normally, pinch rolls or the like engage the congealed or solid ingot at the lower endof the 'mold, which rolls are driven by an electric motor, to assist the constant and uniform movement of theingot through the mold'itself. Even such motor and pinch rolls are'ina s'u fiicient to prevent the ingot from freezing'u'pin the mold cavity.

Thepresent invention contemplates improved apparatus and methods for overcoming all of the above refame to difliculties, which is simple in operation, and effective.

In accordance with the present invention, sensing means to the forces required to control the movement ofthe ingot from the mold are provided which will indicate either a ne ed 'for or an excess of lubricating material, in combination with means for controlling the'fiow of lubri'cating material to the mold.

'Thesensing means may be apparatus 'for indicating increases 'or decreases in the forces required to withdraw or restrain the ingot from the mold above or below a predetermined value, as the case may be. Automaticbr manually controlled means may be provided for adjusting the flow of flux in relation to the variation of the driving force above or below the predetermined level.

The principal object of the invention is the provision of'ia new and improved means for lubricating .the continuously moving billet in a continuous casting operation.

Another object of the invention is .the provision-ofa newfan'dimproved apparatus for properly lubricating the billet in a-continuous casting operation.

"Another'object of the invention is the provision for an improved apparatus for automatically adjusting the flow of lubrication to a continuous casting operation in proportion 'to the need for such lubrication.

The invention may be embodied in certain parts and arrangements of parts, a preferred embodiment of which States Patent (3 'will be described maetan in this application and shown in the accompanying drawing, which is a part hereof, and wherein:

Thesingle figure shows a somewhat schematic diagrain of a continuous casting apparatush'aving automatic means for controlling the supply of lubricating material to the casting operation, all embodying the presentinvention.

Referring now to the drawings wherein the showing is for the purposes of illustrating the 'inventiononly, and not for the purposes of limiting same, the single figure shows a mold 10"having a verticalopen-ended cavity 11, extending throughout the'length thereof. Molten metal 12 is shown as being'poured from a tundish 13 into the upper end of the cavity 'll, and asolidified ingot 15 is shown being withdrawn from the lower end of the cavity 11 by means of pinch rolls 16 which are conventional in the art, driven by an electric motor 17.

The mold 10 is artificially cooled by means not shown. Normally, the molds will have water jacketed surfaces.

The molten metal 12 is puddled in the top of the mold cavity 11, andas the heat vis removed from the molten metal, the metal congeals, moves downwardly through the cavity 11, and is solid or mostly. solid as it leaves the lower end of the cavity 1'1.

It is necessary that the surfaces-of theingot 15 be in relatively close contact with the surfa'ces-ofthe cavity 11 to provide good conduction- 0f 'h'e'at from the molten metal to the mold walls. A'lubricant in the for'mof a powdered fiuxing agent 20 is fed-into the :top of the cavity 11 simultaneouslywith-the molten metal '12. 'This lubricant 20 melts in the #heat of the molten ine'ta'l and completely'covers the'upper surface thereof. Also, the lubricant 20 flows downwardly between the sides of the ingot 15 and the surfaces .of-the:cavit-y 11, to'pro vide a lubricating action from one end-ofzthe cavity 11 to the other. This lubricant must'obviouslymelt at a tempera ture substantially below the solidifying 'temperature of the steel and must provide a lubricating action.

Glass, borax or other known lubricants may be employed, including the hydro-.carbongases which break down in the presence of the heat of ;the molten metal'to provide carbon in th'efree state which-senves asalubricating agent. Obviously,'the lubricant may be introduced into 'the mold ,cavity-in any known-' or. desired manner. For example, the hydro-carbon gases are normally introduced into the mold cavity through'iopenings midway of the length of the cavity. In the embodiment shown, lubricant or flux in granular form is supplied irom a convenient source, such as a :hopper 26 through a control valve 27.

The motor 17 is shownfiin the embodiment of' the -invention as being an alternating current motor, and will generally be of the variable speed'type,*so that the speed of movement of theingot through themold =10 may be readily controlled. Obviously a D. C. motor'could' beemployed, if desired. The motor'17 is shown as being energized from any suitable alternating currentpower source 22 through an tammeter 23, .anda-n' irnpedance 24, shown as a resistor, having a relatively'lowresistance value.

In one embodiment of the inventiorn'the apria'ratus i-sstarted, and the motor 17 energizedto'drive the pinch rolls 16 and pull an ingot from ".the mold cavity 11.

The forces required to pull the ingot 15from the mold 10 under the proper lubricating conditions require a certain amount of currentsuppliedzto the-motor 17, which current is indicated by the ammeter 23. This current will have a predetermined'value forthe ideal operation of the ;apparatus; 2 and by: ideal is meant when the proper" amount of lubricant 20 is being supplied to the casting operation. Should the lubricant supply be insufficient,

ing an increase the current indicated by the meter 23, will open the valve 27 to permit a greater How of lubricant into the upper end of the cavity 11.

In the event that an excessive amount of lubricant 20 is supplied to the cavity 11, the force required to advance the ingot through the mold cavity 11 will decrease, and there will be a decrease of current as indicated by the meter 23 below the predetermined amount. The valve 27 will then be closed partly to cut down the supply of lubricant until the current flow, as indicated by the meter 23, has returned to the predetermined value.

In a preferred embodiment of the invention, means are provided for automatically controlling the opening of the valve 27 in response to the need of the casting operation. Thus, the valve 27 is shown as being operated by a motor 30. This motor is energized from an electronic amplifier 31 of conventional known type. Its exact circuit will not be detailed further herein. The amplifier is energized by a control voltage developed by changes in the voltage across the impedance 24, resulting from changes in the current flowing therethrough to the variations in the force required to remove the ingot 15 through the mold. This voltage is supplied to the amplifier 31 through wire 33 and wire 34, the wire 34 being insulated from the motor circuit by a resister 35.

The voltage across the resister 24 will thus appear between the wires 33 and 34.

To provide a reference voltage, a potentiometer 36 is connected across the terminals of the power source 22. This potentiometer has an adjustable arm 37 connected to the wire 34 through an isolating resister 38.

When the predetermined current is flowing to the motor 17 for proper lubrication of the mold cavity 11, a predetermined voltage drop appears across the impedance 24 which also tends to appear between the wires 33, 34. The potentiometer arm 37 is adjusted to provide a similar reference voltage, which is also fed to the amplifier 31. When the voltage appearing across the resister, 24 is the same as the reference voltage provided by the potentiometer 37, the valve 27 is opened to a predetermined amount. Should the amount of lubricant supplied to the mold cavity 11 be insufiicient, a greater force will be required to advance the ingot 15 out of the mold, thus requiring a greater current flowing to the motor 17. This greater current results in a greater voltage drop across the resister 24 which increased voltage drop is amplified by the amplifier 31 to cause the motor to operate to open the valve 27 further to permit a greater supply of lubricant 20. As the extra lubricant supplied overcomes the sticking problem of the ingot in the mold, the current drawn by the motor 17 will return to normal, and the voltage across the resister 24 will return to be the same as the reference voltage supplied by the potentiometer 36. When this condition exists, the motor 30 willbe stopped, and no further changes in the supply of lubricant will result. If, however, too much lubricant is supplied, the forces required to advance the ingot through the mold will decrease, thus resulting in a decreased'current to the motor17. This results in a lower voltage drop across the resister 24, which change is sensed by the amplifier 31, and the motor 30 is again actuated to close the valve 27 part way and reduce the supply of lubricant 20.

The invention has been described in connection'with a preferred embodiment, although the actual showings have been somewhat schematic. as it believed that the actual apparatus for carrying out the invention may take any one of a number of different forms. The primary thing is that some means he provided for sensing variations in the forces required to advance the ingot 15 through the mold, and that such variations in the forces be interpolated into a variation in the supply of lubricant or flux to the continuous casting apparatus, whereby the amount of lubricant supplied can always be at the optimum value, and seizure of the ingot within the mold or the use of excess lubricant can be entirely avoided.

Obviously, variations in the forces required to advance the ingot 15 through the mold 10 can be detected by measuring the weight of the downward forces in the mold cavity, and controlling the supply of lubricant in response to this variation of weight. Such a method would also work because it will be seen that as an ingot tends to either move more freely through the mold 10, or to move with greater difliculty, the downward forces in the mold 10 will vary in a like manner.

It will be appreciated that alterations and modifications will occur to others upon a reading and understanding of this specification, and it is my intention to include all such modifications and alterations insofar as they come within the scope of the claims.

Having thus described my invention, I claim:

1. In continuous casting apparatus, means for forcibly withdrawing a solidified ingot from a mold at a generally constant speed, means for introducing a lubricating material between the walls of the mold and the solidifying ingot, means responsive to variations in the force required to advance the ingot through the mold at such speed and operatively connected to said second mentioned means for varying the amount of lubricant supplied in direct proportional relationship to such force.

2. A continuous casting apparatus, comprising in combination a mold, means for supplying a lubricant to the mold, and means for withdrawing ingot out of the mold at a generally constant speed, the improvement which comprises means for sensing variations in the forces required to move the ingot through the mold at such speed, and means responsive to the sensing means for controlling the supply of lubricant in direct proportional relationship to variations of such force.

3. The method of controlling the supply of lubricant through a continuous casting operation wherein means are provided for withdrawing the solidified ingot out of the mold, at a generally constant predetermined speed comprising varying the amount of lubricant supplied in response to variations in the amount of force required to advance the ingot out of the mold at such constant speed.

4. A continuous casting apparatus, comprising an elongated mold, means for supplying molten metal to one end of the mold, means for supplying lubricant to lubricate the passage of the molten or solidified metals, as the case may be, through the mold, means for moving the ingot through the mold at a generally constant speed, means for sensing variations in the forces required to move the ingot through the mold at such speed, means responsive to the sensing means for controlling the supply of lubricant in relation to the variation in direct proportion to the force.

References Cited in the file of this patent UNITED STATES PATENTS 2,058,447 Hazelett Oct. 27, 1936 2,135,183 Junghans Nov. 1, 1938 2,225,373 Goss Dec. 17, 1940 2,376,518 Spence May 22, 1945 2,561,360 Goss July 24, 1951 2,709,842 Findlay June 7, 1955 2,747,244 Goss May 29, 1956 FOREIGN PATENTS 493,231 Belgium Ian. 31, 1950 

